1. Field of the Invention
This invention relates to a device for facilitating mounting and removal of polishing wheels in machines for polishing stones or like materials.
2. Description of the Prior Art
As a general rule, machines of this type comprise one or a number of carriages each equipped with a polishing head which comprises a number of polishing wheels. These wheels are removably mounted on the different rotary shafts of the polishing head. To this end, each polishingwheel is usually fixed by bonding to a support in the form of a disk or plate which is in turn fixed by screwing on one of the rotary shafts of a polishing head.
As the work proceeds, it is necessary to replace the polishing wheels by other wheels which have a different grain size (grit). Thus provision has to be made for five wheel changes as well as replacement of polishing wheels which have become dulled during a work cycle. However, screwing and unscrewing of wheel-holding plates involve a number of tedious manual operations which entail the need to withdraw the machine from service over considerable periods of time.
For the reason just mentioned, different wheelmounting systems have recently been proposed for the purpose of reducing the length of time required for carrying out these manual wheel-changing operations.
Thus French Pat. No. FR-A 2,357,333 describes a wheel-holding device comprising series of jaws pivotally mounted on a support fixed on the rotary shaft of a polishing head and adapted to clamp the upper end of a polishing wheel. These jaws are accordingly controlled by a ring attached by screwing to their support and capable of clamping these latter against the upper end of a wheel. Means are also provided for causing resilient opening of the pivotal jaws when the clamping ring is moved to the released position.
French Pat. No. FR-A 2,484,889 describes a device of rather similar type. This device comprises a series of resilient claws for gripping the upper end of a wheel or more precisely the frusto-conical collar of a wheel-holding plate which is separately mounted on a wheel of this type. These claws are carried by a support fixed on the rotary shaft of a polishing head and normally tend to withdraw outwards to the open position. However, the clamping action of said claws can be produced by means of a movable operating member in the form of a ring which is subjected to the action of a thrust spring.
In both instances, however, the systems just mentioned still require a certain number of manual operations for mounting and removing polishing wheels one after the other, which always takes a considerable length of time. Thus in the case of the system described in French Pat. No. FR-A 2,484,889, removal of a wheel calls for the use of a special tool in the form of a tong unit for moving the clamping ring away from the claws in order to permit resilient withdrawal of these latter for the purpose of releasing the corresponding wheel.
Furthermore, the basic design concept of these clamping systems does not permit any possibility of automation of operations which involve mounting and removal of wheels with respect to a polishing head.